Preservation of wood with phenol formaldehyde resorcinol resins

ABSTRACT

Wood and other cellulose-based products are preserved with a water-based treating solution containing a phenolic resin prepolymer such as phenol formaldehyde resin prepolymer, a resorcinol formaldehyde resin prepolymer and water. The treatment is carried out by exposing the wood or other cellulose-based product, while submerged in the treating solution, to one or more cycles of reduced pressure (i.e. vacuum) and elevated pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the preservation of wood, and includes thechemical compositions used to treat the wood, the process of treatingthe wood, and the treated wood that results from the process. Thechemical compositions which are described herein are especially wellsuited for use in the method of U.S. Pat. No. 3,968,276 in which wood tobe treated is exposed to a reduced pressure for the purpose of removingmoisture and volatiles from the wood, and thereafter impregnating thewood with an aqueous phenol formaldehyde/resorcinol formaldehydechemical composition as hereinafter described.

2. Description of the Prior Art

Wood is one of the oldest materials known to man. Its ready availabilityin most parts of the world, coupled with the ease with which it can becut and fabricated into useful articles, makes it well suited for avariety of applications. However, because wood is a cellulosic material,it is susceptible to decay and deterioration over any extended period oftime. As a result, numerous methods have been proposed for treating woodto improve its durability, particularly when used under conditions wherethe wood is exposed to moisture or biological attack.

Applications of wood such as its use in manufacturing railroad ties,utility poles, fence posts, and the like, have created substantialincentives for industry to develop effective and commercially practicalmethods of treating the wood to extend its useful life (i.e. woodpreservation). Various techniques of wood preservation have been usedincluding surface coating, surface treating and pressure penetration ofthe wood with a variety of chemicals such as creosote, halogenatedphenols such as pentachlorophenol and the like.

When halogenated phenols such as pentachlorophenol are used to treatwooden poles (such as utility poles), it is common to dissolve thepentachlorophenol in a hydrocarbon oil, pressure treat the poles, andthen evaporate the excess oil. Such a process is relatively expensive,but is justified by the wood preservative properties of thepentachlorophenol.

However, the treated poles tend to "bleed" their treating solution intothe surrounding soil when the poles are installed in the ground. Thisdraining or leaching effect is more visible on the sunny side of utilitypoles which drain or bleed faster because the heat from the sun warmsthe treating solution and reduces its viscosity.

In an effort to reduce treating costs, water is sometimes substitutedfor the hydrocarbon oil, and the pentachlorophenol is used in one of itssalt forms to provide water solubility. However, this approach has anumber of disadvantages and is less preferred than the oil treatment.

Unfortunately, most of the present treating processes (e.g. those usingcreosote, various copper and mercury compounds, or pentachlorophenol),even when operated under significant pressure conditions, do not resultin deep impregnation of the wood. Thus, the wood being treated with anychemical is typically treated to only a shallow depth and, in the caseof logs or poles, very often the degree of penetration does not extendthroughout all of the soft or sapwood, much less penetrate theheartwood.

However, U.S. Pat. No. 3,968,276 discloses a method for treating wood(logs or dimensional lumber), wherein the wood is preserved byimpregnating the wood with chemicals which penetrate substantially tothe core or center of the wood being treated. In the case of logs orpoles, this penetration can be deep within the heartwood and may besubstantially complete.

U.S. Pat. No. 3,968,276 discloses enclosing the wood within a chamber,sealing the chamber, evacuating the chamber slowly so that the wood isexposed to a pressure below atmospheric pressure, introducing in to thechamber a sufficient amount of an aqueous solution of resin prepolymerto immerse the wood and then maintaining the vacuum over the immersedwood for a period of time both to allow the removal of moisture andvolatiles from the wood and to permit the treating solution to enterinto the wood. Thereafter, an additional amount of the resin prepolymersolution is introduced into the chamber (if needed) and the pressure onthe system is increased to super atmospheric pressure to thereby causean even deeper penetration of the treating solution into the wood. Thevacuum and pressure cycle may be repeated one or more times (e.g. 1 to30 or more cycles). When the treatment is completed to the desiredextent, the treated wood is recovered from the chamber. The processdescribed is extremely effective and achieves substantially greaterpenetration of the wood than any other commonly practiced treatingprocesses.

Also it is known in the prior art, as disclosed in U.S. Pat. Nos.4,399,195 and 4,433,031, that one or more known wood preservatives, suchas the halogenated phenols, can be introduced deep into the wood beingtreated and obtain reduced "bleeding" or leaching, by combining the woodpreservative with the method of U.S. Pat. No. 3,968,276 by using aspecial class of treating compositions that are water-based or waterdilutable which permits the benefits of the aqueous resin prepolymersystem of U.S. Pat. No. 3,968,276 to be maintained.

Further, U.S. Pat. Nos. 4,399,195 and 4,433,031 disclose that it ispossible to accomplish deep penetration with reduced bleeding withoutencountering any significant amount of "blooming" which is normallyassociated with aqueous treating solutions of halogenated phenols. Thisblooming effect is caused by the fact that the aqueous treatingsolutions are made from salts of halogenated phenols, which dissolvereadily in water. Because the salts are water soluble, there is atendency for the salts to be redissolved by rain water or ground waterand to migrate easily to the surface of the treated wood where theycrystallize during the subsequent evaporation of the water, causing the"blooming effect".

U.S. Pat. Nos. 4,399,195 and 4,433,031 disclose manufacturing a waterdilutable concentrate or a water-based treating solution which consistsessentially of: (a) a halogenated phenol wood preservative such aspentachlorophenol; (b) a phenolic resin prepolymer such as phenolformaldehyde prepolymer; (c) a coupling or solubilizing agent forenhancing the water compatibility of the concentrate (e.g. methylalcohol or acetone with or without the addition of a surfactant); and(d) water. Optionally and preferably, the disclosed treating solutionscontain organo/metallic salts, especially copper or zinc salts.

In addition, U.S. Pat. Nos. 4,339,195 and 4,433,031 disclose that theability of the prepolymer to cure rapidly and lock the halogenatedphenol deep within the wood can be enhanced by heating the wood at theconclusion of the treatment (e.g. heating the wood with steam) tothereby accelerate the curing of the resin prepolymer.

The term "curing" as used in the previous paragraph is to bedifferentiated from the term "gelling" as used hereinafter in thepresent art. Curing refers to the process by which wood preservativestabilizes once impregnated into the wood. Gelling refers to thesolidification or semi-solidification of the resins forming the woodpreservative during preparation of the wood preservative. Gelling or,more specifically, the time it takes for gelling to occur (gel timetesting) is used in the art as an indicator of resin activity and isused to predict and select curing parameters and characteristics of theresins used in the wood preservative solutions.

While the process for treating wood as disclosed in U.S. Pat. Nos.4,399,195 and 4,433,031 works quite well, the wood treating compositionsof the prior art suffer from the limitations of having a limited shelflife, relatively slow curing times and the requirement of significantamounts of heat to effect curing.

It was also known in the prior art to use water soluble phenolformaldehyde resoles as wood preservatives. Such a resole of the priorart typically gels in approximately 10 to 20 minutes at 121° C. and hasa shelf life of 3 to 6 weeks at 25° C. (measured by its ability toremain infinitely water dilutable).

In the adhesive art (glues, etc., an art distinctly different from thewood preservative art), it was known that resorcinol formaldehyde resinscould be added to or blended with certain water soluble phenolformaldehyde resoles which contain free formaldehyde to react with theresorcinol, wherein the resorcinol functioned to cause more rapidgelling and curing of the adhesive at room temperature. However, theresorcinol formaldehyde modified phenol formaldehyde resins of theadhesive arts were not used as wood preservatives and invariablyexhibited a much shorter shelf life than non-blended resins. Further,the resorcinol modified resins of the adhesive arts were designed tofully cure at room temperature, which is not compatible with the woodpreservative arts, where the resin must be retained in a liquid statefor extended periods both on the shelf and during the impregnationprocess. While curing at room temperature after the impregnation processis complete may be compatible with the wood preservative arts, prematuregelling of the resin solution at room temperature is not. Gelling of theresins in the wood preservative arts is to be avoided because a fullygelled resin cannot impregnate the wood at all, and the large moleculesin a partially gelled resin cannot effectively impregnate the minuteinterstices of the wood and, therefore, cannot penetrate deep into theheartwood, either.

It would be preferred if the known wood preservative resins of the priorart could cure faster and at lower temperatures after impregnation thanthose presently known in the art, exhibit extended shelf life butwithout premature gelling. Also, while free or unreacted formaldehydemay be necessary with phenol formaldehyde resins of the prior art forreaction purposes, it would also be preferred if such resins wouldexhibit an extremely low free formaldehyde content during resinformation, during the impregnation process at the wood impregnationplant, and after the wood is cured and used in its final application,because formaldehyde is toxic and is considered an environmental hazard.Further, it would be preferred if such resins exhibited increasedtolerance to the additives which are normally added to these resins toaid in wood preservation and fire retardance.

SUMMARY OF THE INVENTION

Generally, the present invention is directed to a method of preservingand fire-proofing wood utilizing specific chemical compositions. Thepresent invention is also directed to the chemical compositions. Thepresent invention is also directed to the process of producing thechemical compositions. Finally, the present invention is also directedto the wood preserved and fire-proofed.

More specifically, the present invention is directed to a waterdilutable concentrate or a water-based wood or cellulose treatingsolution comprising:

a) an effective wood preserving amount of a phenolic resin prepolymer;and

b) an effective amount of resorcinol formaldehyde resin prepolymer.

In a preferred embodiment of the invention, the phenolic resinprepolymer is a phenol formaldehyde resin prepolymer. Optionally andpreferably, the treating solution also contains additives which aid inwood preservation and fire retardance.

The wood treating solution of the present invention unexpectedlyexhibits extended shelf life with reduced premature gelling, fastercuring time, lower curing temperatures, lower free formaldehyde contentand increased tolerance to the additives which are normally added totreating solutions to aid in wood preservation and fire retardance.

Further, the inventors believe that since resorcinol has far morereactive cites than phenol, more cross linking occurs with the phenolformaldehyde/resorcinol formaldehyde resins of the present invention,than the unmodified phenol formaldehyde resins of the prior art and thisadditional cross linking will render the phenol formaldehyde/resorcinolformaldehyde treated wood more impervious to water and more chemicallystable. The inventors believe the increased chemical stability alsoreduces the risk of formaldehyde emissions from the treated wood orother cellulosic products.

Further still, the inventors believe that the cross linking of thephenol formaldehyde/resorcinol formaldehyde resins of the presentinvention provides more bonding with the cellulose, which in turnentraps in the treated wood the water soluble additives which enhancewood preservation and fire retardance, even after the treated wood iscured. These water soluble additives can penetrate deeply into theheartwood for greater protection of the wood. In contrast, for example,the prior art copper compounds were typically not water soluble but wereemulsified in water, and these large emulsified copper molecules couldonly impregnate the wood superficially, i.e. approximately 0.25-0.5inches, as opposed to penetrating deep into the heartwood.

DETAILED DISCUSSION

The present invention is directed to aqueous resin solutions fortreating wood and the use of such solutions to treat wood (both driedwood and green wood), and the resulting treated wood products.

In the following discussion, the term "treating solution" refers to theaqueous resin solution comprising a phenolic resin prepolymer and aresorcinol formaldehyde resin prepolymer. When wood preserving compounds(such as copper-based compounds) are added to the aqueous resinsolution, the resulting compound is referred to as a wood preservativesolution. When fire retarding compounds (such as diammonium phosphates)are added to the aqueous resin solution, the resulting compound isreferred to as a fire retarding solution. When both wood preservingcompounds and fire retarding compounds are added to the aqueous resinsolution, the resulting compound is referred to as a woodpreserving/fire retarding solution.

In the wood preserving and fire proofing industry, it is commonly thecase that a resins manufacturer will manufacture the basic resintreating solution and provide that solution to a wood treating plant orfacility which will then add the wood preserving and/or fireproofingcompounds during the wood impregnation process.

For convenience, it is sometimes convenient to make the treatingsolution of the present invention in two steps, the first step being thepreparation of water-dilutable concentrate or syrup, and the second stepconsisting of diluting the concentrate with water to achieve a desiredconcentration of active ingredients. Although any distinction betweenthe concentrate and the aqueous treating solution, per se, is to acertain extent arbitrary, the treating solution of the present inventionnormally contains from 8% to 30% by weight of an aqueous phenolic resinprepolymer, 0.8% to 7% by weight resorcinol formaldehyde resin, and 64%to 91% by weight of water. By comparison, the water dilutableconcentrate or syrup generally contains from 40% to 60% by weight of thephenolic resin prepolymer, 4% to 12% by weight resorcinol formaldehyderesin, and 28% to 56% by weight of water.

FORMATION OF THE AQUEOUS PHENOLIC RESIN PREPOLYMER

While the phenolic resin prepolymer component of the aqueous resintreating solution of the present invention includes other phenolicderivatives and other formaldehyde derivatives, the preferred phenolicresin prepolymer is a phenol formaldehyde resin prepolymer and isformulated beginning with the phenol in its liquid state.

Formaldehyde is added to the molten phenol in a mole ratio ofapproximately 1.0 to 2.75 moles per mole of phenol. Exceeding the upperlimit causes excessive amounts of free formaldehyde, while going belowthe lower limit results in a resin solution incapable of effective crosslinking. Either liquid solutions of formaldehyde or formaldehyde prillscan be used with the present invention. Typically, 91% paraformaldehydeprills are added to the phenol and melted in the reaction vessel.Paraformaldehyde prills are preferred because they eliminate the need toremove excess water from the resin after it has been produced. There islittle or no reaction between the molten phenol and formaldehyde until areaction catalyst is added. The catalyst typically causes a strongexothermic reaction.

Catalysts compatible with the present invention include alkaline earthhydroxides and carbonates, including sodium hydroxide, sodium carbonate,potassium hydroxide, potassium carbonate, barium carbonate and calciumcarbonate. Sodium hydroxide is the preferred reaction catalyst and isadded to the reaction vessel preferably as a 50% solution in waterwithin the range of 0.02 to 0.12 moles per mole of phenol. Exceeding theupper limit causes an excessively exothermic reaction while going belowthe lower limit will excessively slow the rate of reaction and causeincomplete curing. Water is added to temper the exothermic reaction.

The above components, phenol, formaldehyde, sodium hydroxide and water,are reacted between 50° C. to 100° C. for approximately 0.5 to 6 hours,preferably at about 65° C. for 2 to 4 hours, and subsequently adjustedwith water to a non-volatile (or solids content) of 50% to 70%.

The phenolic resin prepolymer is a clear to amber colored water solubleliquid. Low viscosity aqueous phenolic resin prepolymers are preferredfor ease of use. Such prepolymers typically have molecular weights ofless than 1000.

FORMATION OF THE RESORCINOL FORMALDEHYDE RESIN PREPOLYMER

The second component of the present invention, the resorcinolformaldehyde resin prepolymer, is formulated beginning with theresorcinol.

Formaldehyde is added to the resorcinol in a mole ratio not exceeding0.70 moles per mole of resorcinol. The mole ratio of resorcinol toformaldehyde is important in the present invention. The mole ratio isselected to ensure an excess of resorcinol in the resorcinolformaldehyde resin prepolymer. The excess of resorcinol in turn ensuresthat there are no aldehyde radicals present in the resorcinolformaldehyde resin prepolymer. The absence of aldehyde radicals ensuresthat the resorcinol formaldehyde resin prepolymer can be readily handledand can be controllably reacted with the residual formaldehyde in theaqueous phenolic resin prepolymer when the two prepolymers of thetreating solution of the present invention (aqueous phenolic resinprepolymer and resorcinol formaldehyde resin prepolymer) are blendedtogether as discussed below. Exceeding the upper limit of this moleratio will also result in an undesirable premature solidification of theresorcinol formaldehyde resin prepolymer.

Either liquid solutions of formaldehyde or formaldehyde prills can beused with the present invention. Typically, 91% paraformaldehyde prillsare added to the resorcinol and melted in the reaction vessel.Paraformaldehyde prills are preferred because they eliminate the need toremove excess water from the resin after it has been produced. There islittle or no reaction catalyst between the resorcinol and formaldehydeuntil a reaction catalyst is added. The catalyst typically causes astrong exothermic reaction.

Catalysts compatible with the present invention include alkaline earthhydroxides and carbonates, including sodium hydroxide, sodium carbonate,potassium hydroxide, potassium carbonate, barium carbonate and calciumcarbonate. Sodium hydroxide is the preferred reaction catalyst and isadded to the reaction vessel within the range of 0.02% to 0.12% molesper mole of resorcinol, about 0.045 moles being preferred by weight.

Water is added to temper the exothermic reaction.

The above components, the resorcinol, formaldehyde, sodium hydroxide andwater are reacted to completion at a temperature of approximately 50° C.to 100° C. for a period of from 0.5 to 6 hours, preferably at 65° C. for2 hours and adjusted to a 50% to 75% solids content and, morepreferably, to a 60% solids content. The resorcinol formaldehyde resinprepolymer of the present invention is an aqueous dark red liquid and isreactive in the presence of formaldehyde or formaldehyde donors.

FORMATION OF THE TREATING SOLUTION OF THE PRESENT INVENTION

The phenolic resin prepolymer is then blended with the resorcinolformaldehyde resin prepolymer to yield the treating solution of thepresent invention. More specifically, the resorcinol formaldehyde resinprepolymer is added in a ratio of 10% to 30% by weight of the phenolicresin prepolymer, preferably 16% to 20%. The two components are simplyblended, and no heat is applied at this point. Exceeding the upper limitof this weight percent may result in an unstable compound, while goingbelow the lower limit of this weight percent causes an unreactivesystem. Surprisingly, the treating solution of the present inventionexhibits considerably longer shelf life than blends known in the art asdiscussed in detail below. Typically, the treating solution of thepresent invention will be manufactured to this point by a resinsmanufacturer, who will then ship the treating solution to a woodpreservation plant, where the solids content of the treating solution isadjusted to 8% to 36%.

It has been found with the present invention that the addition ofapproximately 2 to 6 parts by weight of hexamethylene tetramine to 100parts of the treating solution of the present invention furtheraccelerates the gel time and cure rate, but at the expense of storagelife. It is believed that at elevated temperatures, the hexamethylenetetramine decomposes to produce ammonia and formaldehyde, which also actto accelerate the reaction. It is not known why the addition ofhexamethylene tetramine shortens shelf life.

IMPREGNATION OF WOOD WITH THE TREATING SOLUTION OF THE PRESENT INVENTION

In treating wood, the treating solution of the present invention will beprepared as described above, at an appropriate solids content level(i.e. the appropriate level of dilution) and the wood will beimpregnated by methods known in the art, particularly the method taughtby U.S. Pat. No. 3,968,276, which will typically include the followingsteps:

1. Wood to be treated is selected for treatment. The wood will bedebarked and usually precut (e.g. dimension lumber) or pre-shaped (e.g.poles or fence posts). It may be green or air-dried or force dried andwill often be in the form of poles or dimensional lumber. The ability totreat green wood (e.g. wood containing a significant amount of naturalmoisture) is an important advantage of the present process.

2. The wood to be treated is placed in an evacuation zone and exposed topressures which are below atmospheric pressure (e.g. at a vacuum of atleast 20 inches of mercury, preferably at least 26 inches of mercury)for a time sufficient to remove moisture and other volatiles from thewood. Vacuums of at least 28 inches of mercury are preferred. Thisreduced pressure is usually achieved slowly over a period of from 10 to120 minutes (preferably 15 to 60 minutes).

3. The wood is then immersed in or flooded with the treating solution ofthe present invention while still under reduced pressure. During thisphase of the treating, additional water and volatiles escape from thewood, and the treating solution begins to penetrate into the wood.

4. The pressure within the treating chamber or zone is then graduallyincreased to a level above atmospheric pressure (e.g. often to a levelof 25 psig-500 psig, preferably 50 to 350 psig) to thereby increase thepenetration of the wood by the treating solution. Typically, this stepis continued until the treating solution has substantially completelypenetrated into the heartwood, although the process could of course bestopped short of that point if a lesser treatment is desired.

5. To further improve and enhance the depth and quality of penetrationof the treating solution into the wood, the vacuum and pressure cyclecan be repeated as many times as desired (e.g. 2 to 25 or more cycles).When the process is cycled in this fashion, it is helpful if the maximumpressure during each cycle is increased each time by, for example,10-100 psig above the maximum pressure of the previous cycle (usually apressure increase of 25% to 100% over the previous pressure). Thisappears to prevent the rupture and collapse of the wood cells near thesurface of the wood.

6. Recovering the treated wood from the treating chamber.

Note that the vacuum and pressure phases of the treating cycle should beachieved gradually to avoid destruction of the cell walls of the wood.Thus, while speed is important for commercial purposes, too rapid achange in the pressure can be harmful. Consequently, the optimum cyclerates, pressure and vacuum should be determined for each set ofoperating conditions to be used (e.g. size, shape and type of wood to betreated; composition of the treating compositions, temperature, etc.)

Since it is the intention of the present invention to cause or permitthe treating solution to cure after it has penetrated deep within thewood, the conditions of treating should be made so as to permit easypenetration of the wood followed by a rather rapid curing of thetreating solution after penetration. It has been discovered that onevery convenient method of accelerating the curing of the treatingsolution after the treating solution has deeply penetrated into the woodis to heat the treated wood. Although this heating can be accomplishedin a variety of ways, the direct application of steam to the treatedwood is preferred. This method requires no special chemicals and avoidsthe problems of premature curing that are sometimes associated with theuse of catalysts. Moreover, the use of steam is convenient, economical,environmentally acceptable and does not cause any cleanup problems. Oneof the advantages of the present invention is that less heat and time isrequired to effect curing. The amount of heat and time will vary withthe cross section of wood and the type of wood being cured.

FORMATION OF WOOD PRESERVATIVE SOLUTIONS AND/OR FIRE RETARDANT SOLUTIONS

If desired, the treating solution of the present invention and theconcentrates thereof may contain other ingredients such as fireretardant chemicals, dyes or colorants, catalysts, various biocides andother chemicals (e.g. borax, which serves as a buffer or stabilizer).The presence of wood preservatives such as organo-metallic compounds isoptional but preferred. Compounds of zinc and copper are particularlydesirable. Suitable organo/metallic compounds include zinc naphthenate,copper naphthenate and copper-8-quinolinolate. The treating solution ofthe present invention has been successfully tested with the addition ofwater soluble copper (cupric) salts such as copper gluconate and coppertriethanolamine, which function to enhance the wood preservativefunctions of the treating solution. The treating solution of the presentinvention has also been successfully tested with the addition ofdiammonium phosphate, which acts as a fire retardant.

The treating solution of the present invention is also useful in thepreservation and fire-proofing of other cellulose fiber-based products,in phenol formaldehyde resin-sized woven and non-woven products, infiberglass thermal insulation and in pultruded products.

ADVANTAGES OF THE PRESENT INVENTION INCLUDE

1. a faster gel time (reduced 10 to 25 times at 121° C. over prior artcompositions from about 9-20 minutes to instantaneous gelling in theexamples discussed below), which results in faster curing times, whichin turn permits more quality management by allowing full curing at thewood treating plant as opposed to the end user's location--thuseliminating the effect on curing of unpredictable variables such asseasonal effects, geographic effect, etc. at the end user's site;

2. curable at significantly lower temperatures, which in turn lowers thecost of curing;

3. longer shelf life (extended from about 3-6 weeks to about 20 weeks ormore, as shown in the examples discussed below);

4. much lower "free formaldehyde" content (reduced from a range of about0.6-3.9% to a range of about 0.1-0.2% as shown in the examples discussedbelow), which reduces emissions of formaldehyde during "B-staging" andcuring cycles and is preferred from an environmental standpoint as freeformaldehyde is an environmental hazard;

5. increased tolerance to the additives which are normally added tothese resoles to aid in wood preservation (e.g. copper-based additives)and fire retardance (e.g. diammonium phosphate).

The present invention will by further understood by reference to thefollowing Examples.

EXAMPLES 1 AND 2 FORMATION OF AQUEOUS PHENOLIC RESIN PREPOLYMERS

First, two phenol-formaldehyde resins (designated "A" and "B"respectively) were formulated as follows:

    ______________________________________                                                          Ex 1      Ex 2                                              Phenol-Formaldehyde                                                                             Resin A   Resin B                                           ______________________________________                                        Phenol            100 moles 100 moles                                         91% Paraformaldehyde                                                                            130 moles 250 moles                                         Water             200 moles 200 moles                                         50% Sodium Hydroxide                                                                             4.5 moles                                                                              10.5 moles                                        ______________________________________                                    

Resin A was reacted for 2 hours at 65° C. and adjusted with water to anon-volatile (or solids content) of 63%.

Resin B was reacted for 3.5 hours at 60° C. and adjusted with water to anon-volatile (or solids content) of 63%.

EXAMPLE 3 FORMATION OF AQUEOUS RESORCINOL FORMALDEHYDE RESIN PREPOLYMER

A resorcinol-formaldehyde resin prepolymer (designated hereinafter "C"),was formulated comprised of the following:

    ______________________________________                                                           Ex 3                                                       Resorcinol-Formaldehyde                                                                          Resin C                                                    ______________________________________                                        Resorcinol         100 moles                                                  91% Paraformaldehyde                                                                              50 moles                                                  Water              210 moles                                                  50% Sodium Hydroxide                                                                              4.5 moles                                                 ______________________________________                                    

Resin C was reacted to completion at a temperature of 85° C. andadjusted to a 75% solids content by vacuum distillation. Resin C isreactive in the presence of formaldehyde or formaldehyde donors.

EXAMPLES 4 AND 5 FORMATION OF THE TREATING SOLUTION OF THE PRESENTINVENTION

Approximately 15 parts by weight of Resin C was added each to Resins Aand B, resulting in Example 4 (Resin AC) and Example 5 (Resin BC). Acomparison of the properties of Resins A, B, AC and BC appears below:

    ______________________________________                                                    Ex. 1    Ex. 2    Ex. 4   Ex. 5                                   Property    Resin A  Resin B  Resin AC                                                                              Resin BC                                ______________________________________                                        Non-volatile                                                                              63%      63%      63%     63%                                     content                                                                       Viscosity   180 cps  120 cps  250 cps 150 cps                                 pH          9.0      9.0      8.8     8.8                                     Sunshine Gel Time                                                             @ 121° C.                                                                          20 min.  9 min.   13 min. Instantly                               @ 107° C.                                                                          58 min.  28 min.  36 min. 1.6 min.                                Water Tolerance                                                                           infinite infinite infinite                                                                              infinite                                Free Formald.                                                                             0.6%     3.9%     0.2%    0.1%                                    Storage     28 days  40 days  >140 days                                                                             >90 days                                life [1]                                                                      ______________________________________                                    

1. Storage life of the resins were measured by loss of water tolerancefrom infinite to less than 1000% when stored at 25° C. Resins AC and BCremained at infinite water tolerance at the last reported test date.

EXAMPLES 6 AND 7 ADDITION OF HEXAMETHYLENE TETRAMINE TO THE TREATINGSOLUTION OF THE PRESENT INVENTION

A treating solution was formulated according to Examples 4 and 5. Toeach solution was added three parts by weight of hexamethylenetetramine, resulting in treating solutions Example 6 (Resin ACH) andExample 7 (Resin BCH). A comparison of the properties of Examples 6 and7 appears below:

    ______________________________________                                                         Ex. 6       Ex. 7                                            Property         Resin ACH   Resin BCH                                        ______________________________________                                        Non-volatile     63%         20%                                              content                                                                       Viscosity        230 cps     20 cps                                           Ph               8.8         8.7                                              Sunshine Gel Time                                                             @ 121° C. --          --                                               @ 107° C. 6.1 min.    --                                               Water Tolerance  infinite    infinite                                         Free Formaldehyde                                                                              0%          0%                                               Storage life [1] 2 days      17 days                                          ______________________________________                                    

Examples 6 and 7 remained stable with the subsequent addition of watersoluble copper (cupric) salts such as copper gluconate and coppertriethanolamine. The addition of diammonium phosphate to Example 6 waswell tolerated, but, for reasons not known, was not well tolerated byExample 7.

Example 6, containing copper triethanolamine and diammonium phosphate,when impregnated in a cellulose substrate reached a full cure in 3-4hours at 80° C. This wood preservative solution was stable for 2 days at20°-25° C.

What is claimed is:
 1. A treating solution suitable for treating woodand other cellulose-based materials comprising:(a) 8% to 30% by weightof a phenolic resin prepolymer; (b) 0.8% to 7% by weight of a resorcinolformaldehyde resin prepolymer; and (c) 64% to 91% by weight of water. 2.The treating solution of claim 1 wherein said phenolic resin prepolymeris phenol formaldehyde resin prepolymer.
 3. The treating solution ofclaim 1 wherein said phenolic resin prepolymer is present in a ratio of16% to 20% by weight.
 4. A treating solution suitable for treating woodand other cellulose-based materials, wherein said treating solution is awater dilutable concentrate comprising:(a) 40% to 60% by weight of aphenolic resin prepolymer; (b) 4% to 12% by weight of a resorcinolformaldehyde resin prepolymer; and (c) 28% to 56% water.
 5. The treatingsolution of claim 1, further comprising organo-metallic wood preservingcompounds.
 6. The treating solution of claim 5 wherein saidorgano-metallic wood preserving compounds are selected from the groupcomprising copper gluconate and copper triethanolamine.
 7. The treatingsolution of claim 1 further comprising diammonium-based fire retardantcompounds.
 8. The treating solution of claim 7 wherein saiddiammonium-based fire retardant compound is diammonium phosphate.
 9. Amethod of preparing a treating solution suitable for treating wood andother cellulose-based materials comprising:(a) a first step of addingphenol to a first reaction vessel; (b) a second step of addingformaldehyde to said first reaction vessel in a mole ratio ofapproximately 1.0 to 2.75 moles per mole of phenol; (c) a third step ofadding a catalyst to said first reaction vessel in a mole ratio of 0.02to 1.2 moles per mole of phenol, wherein said catalyst is selected fromthe group consisting of alkaline earth hydroxides and alkaline earthcarbonates; (d) a fourth step of adding water to said first reactionvessel; (e) a fifth step of reacting the contents of said first reactionvessel for approximately 0.05 to 6 hours at a reaction temperature of50° C. to 100° C. to form a phenolic resin prepolymer; (f) a sixth stepof adjusting the solids content of the contents of said phenolic resinprepolymer with water to about 50% to 70%; (g) a seventh step of addingresorcinol to a second reaction vessel; (h) an eighth step of addingformaldehyde to said second reaction vessel in a mole ratio notexceeding 0.70 moles per mole of resorcinol; (i) a ninth step of addinga catalyst to said second reaction vessel in a mole ratio of 0.02 to 1.2moles per mole of resorcinol, wherein said catalyst is selected from thegroup consisting of alkaline earth hydroxides and alkaline earthcarbonates; (j) a tenth step of adding water to said second reactionvessel; (k) an eleventh step of reacting the contents of said secondreaction vessel for approximately 0.5 to 6 hours at a reactiontemperature of 50° C. to 100° C. to form a resorcinol formaldehyde resinprepolymer; (l) a twelfth step of adjusting the solids content of thecontents of said resorcinol formaldehyde resin prepolymer with water toabout 50% to 75%; (m) a thirteenth step of blending said phenolic resinprepolymer with said resorcinol formaldehyde resin prepolymer and waterwherein said resorcinol formaldehyde resin prepolymer is present in aratio of about 10% to 30% by weight of said phenolic resin prepolymer toform said treating solution.
 10. The method of claim 9 furthercomprising the step of adjusting the solids content of said treatingsolution to 8% to 36%.
 11. The method of claim 9 further comprising thestep of adding organo-metallic wood preserving compounds.
 12. The methodof claim 11 wherein said organo-metallic wood preserving compounds areselected from the group comprising copper gluconate and coppertriethanolamine.
 13. The method of claim 9 further comprising the stepof adding diammonium-based fire retardant compounds.
 14. The method ofclaim 13 wherein said diammonium-based fire retardant compound isdiammonium phosphate.